Long chain saturated aliphatic amino acids, lactams, and dibasic acids are important monomers for long chain nylons and engineering plastics. Nylons are a class of polymers that contain amide bond on their backbone of chains. Nylons are one of the most widely used, most numerous in types, and most consumed class of engineering plastics.
Because of their unusual molecular structure, long chain nylons possess extraordinary physical properties, i.e., higher mechanical strength than metal, low hygroscopicity, excellent resistance to oil, low temperature, abrasion, and chemical corrosion, and most importantly, easy to fabricate. Long chain nylons are made into many kinds of plastics products, spun to fibers, and stretched to thin films. Long chain nylons are also used in paints and hot melt adhesives. Hence, long chain nylons find wide applications in automobile, electrical, electronic, telecommunications, petrochemical, and aerospace industries.
Long chain amino acids and lactams are used industrially as monomers to produce nylon-9, nylon-11, and nylon-12.
Long chain dibasic acids are condensed with diamines industrially as starting materials to produce nylon-610, nylon-612, nylon-510, nylon-512, nylon-1010, and nylon-1212.
WO 2017/088218 and the co-pending U.S. Ser. No. 15/601,556 both by the present inventor, both of which are incorporated by reference herein, disclose a novel process for the coproduction of long chain amino acids and dibasic acids from keto fatty acid derivatives. According to the disclosed process, long chain keto fatty acid derivatives are reacted with hydroxylamine to form an oxime derivative, which is subjected to the Beckmann rearrangement to yield a mixture of two amide derivatives. These amide derivatives are hydrolyzed to a mixture of products containing long chain amino acids and dibasic acids, which are isolated by a process of step-wise neutralization in a highly dilute concentration. Thus, a substantial amount of energy is required for the concentration, so that the process is not economical.
Moreover, the present inventor has found that long chain amino acids and dibasic acids of required quality for the production of polyamides cannot be obtained, if the process according these prior disclosures is applied for commercial starting materials, which contain various amount of other fatty acids. Apparently, these impurities contaminate intended products and thus demand a process for their removal from final products of required purity.
Hydrolysis of the mixed amide derivatives from the Beckmann rearrangement yields not only long chain amino acids and dibasic acids, but also short chain alkyl amines and alkanoic acids. There is a lack of any method for the separation and recovery of these short chain products from the mixture of the hydrolysis reaction.
It is desirable to have a process for the separation of each component to their required purity from their complex mixture to achieve an economical process and to reduce or eliminate the disposal of waste stream.
It is an object of the present invention to disclose a process for the separation of long chain amino acids, dibasic acids, short chain alkyl amines, short chain alkanoic acids, and for the recovery of other fatty acids present in the commercial starting materials, such as stearic acid, and impurities generated as byproducts of the production reactions. By the process of the present invention, long chain amino acids and dibasic acids are separated simply, efficiently, and economically with high yields and excellent purity.
It is another object of the present invention to disclose a process for the recovery of long chain amino acids and inorganic salts from aqueous waste mother liquor. As a result, there is no aqueous waste discharge from production process.